DIY Electric Car Forums banner

1 - 20 of 91 Posts

·
Registered
Joined
·
28 Posts
Discussion Starter #1
Hi All... glad to see the new feaure

May I add to the knowledge base some news perspectives that should tickle a few members. There is some recent research that shows the best EV is in fact a Electric hydraulic ev for two very simple reasons: 1) the hydraulics can do regenerative braking at about 60% plus efficiency whereas a EV will be lucky to do 30%. So in town this is maybe a 30% range increase? 2) the hydraulics can be configured to be a 'launch assist" and so can dramatically reduce battery current loads without any compromise in performance, again, more typical in town. so again, "the best EV is in fact a electric hydraulic EV"... comments welcome. Normanbutchgrant
 

·
Administrator
Joined
·
6,137 Posts
If you are talking about very low speed machinery - 10 mph or less
Then you are quite correct!

At normal road speeds the losses in hydraulic systems rapidly get overwhelming
 

·
Registered
Joined
·
28 Posts
Discussion Starter #3
Hi Duncan... actually not at all limited to low speed.

The research shows that even using a fully hydrostatic drive ( which is probably the worst case) that the results were significantly better than a pure EV... there is other work out there but the easiest is to look up is a guy "Jia-Shiun Chen" and his work...

Basically the Electric Hydraulic version outperformed the pure EV in virtually every aspect?

" The best electric vehicle is in fact a electric hydraulic vehicle" seems well reasoned

It also does not seem that difficult?
 

·
Registered
Joined
·
131 Posts
it is always better to minimize brake usage, even with regen. For my driving style the difference would never pay for itself, even if it was dirt cheap.

Plus your figures are kind of random (hardly counts as adding "knowledge"), fwd regen can do a lot better than %30, 4wd even better. And the state of the art is constantly evolving.

Hydraulic regen isn't even specific to EV's. Plus it is tricky enough to make seamless transitions between regen and friction brakes already. You gonna add a bypass valve to control the hydraulic part? There goes all your efficiency. A wobble plate big enough to stop a car loaded with batteries (and a hydraulic tank and an accumulator)? Where you gonna put that stuff anyway?

Maybe if the post was less pretentious and more fact based.

not even a link to the "research" you are quoting...
 

·
Administrator
Joined
·
6,137 Posts
So a hydraulic vehicle outperformed an EV?

As an engineer I find that very hard to believe - maybe it outperformed the EV that he built?

There are simply too may losses in a hydraulic system - and almost no losses in an electric system

The reason that you only get about a 10% range improvement from re-gen braking is NOT for the inefficiencies - it's over 80% efficient - but simply because there is very little energy going into the brakes - unless you drive like a hooligan

Do the numbers - calculate just how much energy you can store in a hydraulic accumulator - it's actually quite disappointing - enough for re-gen but not enough to actually drive somewhere

So you end up needing batteries and electric motors - the hydraulic drive then becomes just another parasitic load
 

·
Registered
Joined
·
28 Posts
Discussion Starter #6
Hi Steveob

I just did give some info on how to get some of the research data as a intro. I thought this would be quite a interesting discussion point for members to consider...


I note your comments on my motive... but I take your point
 

·
Registered
Joined
·
28 Posts
Discussion Starter #7
hi again Duncan

The simulations in the research account for all the issues you mention and STILL "the best EV is a electric hydraulic EV" when the results are analysed.

It may be simulations, but it is proper R&D

uhm... as a the engineer you state " almost no losses in an electrical system" is simply not true... The electric motor has a efficiency map ( not that different to hydraulic motor), then the inverter has a efficiency map and then the batteries (depending on the chemistry) have losses both with charge in and charge out. so no, it not true

I am trying to keep this a a lively debate for members too
 

·
Registered
Joined
·
131 Posts
I thought this would be quite a interesting discussion point for members to consider...
If you find a torque/rpm vs efficiency graph for an existing motor (and additional plumbing and control), come talk to me, because there won't be anything to discuss if we just LOOK at the data.
 

·
Registered
Joined
·
28 Posts
Discussion Starter #9
wow...and you say I am pretentious...

I have done so... somehow I dont get how you cant disregard research that you could simply look up and confirm yourself instead of trivializing what is actually quite exciting developments in the field......

These are such obvious observations you ask me to redo and answer to you ....... wow again..... each and every point you have raised is dealt with if you would at least be open to look at the research

( to misquote monty python " I can argue in my spare time")

Do you not think that proper R&D and published papers are worth at least
looking at on your own time before making such authoritarian ( but wrong) comments
 

·
Registered
Joined
·
131 Posts
You made a claim and refused to back it up. I'm not in the habit of validating every claim made on the internet, it is your responsibility to provide supporting evidence. I don't know what you are looking at even or how you drew your conclusions.

Yes, quite presumptuous of you to think I should "google it" when what you are saying doesn't make any sense.
 

·
Registered
Joined
·
28 Posts
Discussion Starter #11
well, that is your choice made... I trust other members may find more value in this discussion than you have.

yes, " The best EV is a electric hydraulic EV" ... based on proper research after all!
 

·
Administrator
Joined
·
6,137 Posts
Ok
First have you done the energy calculations?

I will assume that you have and that you will understand that a hydraulic accumulator cannot replace the battery

So now I have two models
One goes
Battery - source
Inverter - 95%
Motor -90%
direct drive - 98%
wheels
Overall - 84%

The other one goes
Battery - source
Inverter - 95%
Motor - 90%
hydraulic pump - 80%
Pipes - 96%
hydraulic motor - 80%
Direct drive - 98%
wheels
Overall - 51%

You simply can't get to the efficiencies of the electric model because the hydraulic bits are "extra" - additional conversion stages for the gods of thermodynamics to take their cut


Now a hydraulic system on an IC engine can make sense - but on an EV it's simply not going to help

Especially as the re-gen system on an EV uses no additional parts and has an overall efficiency

wheels-
direct drive - 98%
Motor -90%
Inverter - 95%
Battery - source

Overall efficiency 84%
The range improvement will vary from 15% to less than 5% - but that is simply due to the amount of braking that you need - and will be the same no matter what you use

You are simply NOT going to get any better than that - your hydraulic system is going to be worse
 

·
Registered
Joined
·
28 Posts
Discussion Starter #13
Hi Duncan, you really do misrepresent me and the research I allude to. Chen is a independent researcher.

Please just consider the potential value of what this thread. I am trying to promote what looks like a real paradigm shift that is not really difficult to implement either

research is research.. "like a box of chocolates, you never know what you gonna get"

for example, the Chen ( he is not the only one) research uses Matlab models that are proper physical models of engines, batteries , hydraulics etc and while his published research only plots against a few drive cycles, similar results are seen in virtually all other drive cycles. The Chen version is actaully not even a particularly good design yet even with that "the best EV is in fact a electric hydraulic EV"

are you really asserting that the Matlab models are unrealistic?

this is actually quite exciting stuff
 

·
Administrator
Joined
·
6,137 Posts
Yes
I am saying that any model that adds some ADDITIONAL conversion stages - and purports to get better efficiency is by definition a load of bollocks!

Your Hydraulic EV still needs the
Battery
Inverter
Motor
Dive to wheels

Those simply don't change

Then you ADD -
Hydraulic Pump
Pipes
Hydraulic Motor

Every time you convert the gods take a cut!

You have NOT eliminated any of the existing inefficiencies

And you have ADDED three big ones

IC engines have large ranges of efficiencies - so you can sometimes get a benfit

But Inverters and electric motors do not have such a large range
In the normal operation zone it is about 85% to 90%

The only way that you could build a hydraulic EV with higher efficiency would be by comparing it to a normal EV that was being run miles outside the design parameters

I could build you a hydraulic EV that was more efficient at 4 mph than a Tesla at 4 mph
BUT only because the Tesla is not built to run at 4 mph

If you use any modeling software or system you should always do a sanity check on it -

I have often seen excellent expert systems give ludicrous results because the person using them has not understood how they were set up and has asked the system to do something that the original programmer did not think would ever be asked

Use modeling systems - but always be aware of GIGO - always do a sanity check
 

·
Registered
Joined
·
28 Posts
Discussion Starter #15
How do i state politely that you are simply wrong? I dont think there is a way..... I guess this whole thread will now be deleted as you have the admin buttons to do so.

I guess its time to state that I actually am heavily involved in this field and am very well suited to make the statements both from a theoretical and practical point ...

There are benefits in the regenerative braking and electrical optimization that will ( have) result in results predicted.....

ah well. I least i know I tried...

" So long, farewell, adeu adeu"
 

·
Registered
Joined
·
131 Posts
zero knowledge to share, just a bunch of hearsay, thanks for absolutely nothing norman.

Given how improperly this was presented here, I have zero faith that there was "proper research" done in the first place.
 

·
Registered
Joined
·
28 Posts
Discussion Starter #17 (Edited)
well I think I need to thank Duncan for not doing the obvious and just deleting the thread....... was unexpected....

I am correct BTW... yes, I really am ........This is a one enabling technology for EV's and I am rather surprised at the direction this thread took...

Anyway. If anyone else wants to continue this discussion, i will get the notifications and will try respond in a reasonable time
 

·
Registered
Joined
·
131 Posts
I took your advice and googled relevant keywords.

https://www.angelcapitalmarket.com/investment-opportunity/hydraulic-hybrid-transmission-082716

so you are just trolling for "investors" in vaporware, basically selling.

Your opening title is empirically wrong, and you have offered zero empirical data to back it up, heck even suggesting you should is somehow "presumptuous", probably more gimmick to get people to "discuss".

buzz off. Or keep trying to get the last word and see where it goes till the thread gets locked.
 

·
Registered
Joined
·
28 Posts
Discussion Starter #19 (Edited)
steveob I have no idea who you are but you really need to get a grip on reality and what your technical limitations are.... ( Duncan, I really have no need for investors... FYI... we doing great thank you).

do you consider at all that maybe,........ just maybe, I am bring a really cool enabling technology to the group for discussion that i know about and you dont?...

Yip, that is what I am doing...
 

·
Registered
Joined
·
23 Posts
The Ariens Amp battery powered riding lawnmower was designed like that.
Battery powered electric motor driving a Hydrostatic transaxle.
It was total frailer, noisy, low power, short run time.
Hydrostatic transaxle eats up to much power to run compared to a gear driven transaxle.
Basically they tried to use Hydraulic's as a speed controller, instead of a electronic motor speed controller which doesn't have the looses of Hydrostatic setup.
 
1 - 20 of 91 Posts
Top